The present invention pertains to electronic engine spark timing controllers and in particular to a noise immune reset circuit for resetting an electronic spark timing controller of the type having an integrator circuit which is periodically reset at predetermined engine crank angles.
In one type of engine spark timing controller, an integrator circuit provides a crank position signal representative of the engine crank angle. The integrator is periodically reset at predetermined crank angles, for example, being reset every 90.degree. of engine crank angle for an 8 cylinder engine and every 120.degree. of engine crank angle for a 6 cylinder engine. The integrator circuit, therefore, generates a saw-tooth type waveform which is representative of the engine crank angle over the full range of engine operating speeds. In order to achieve optimum performance in such an electronic spark timing controller, it is important that the integrator always be accurately reset. Accuracy in resetting can be attained by rendering the circuit immune to spurious triggering due to extraneous electrical noise picked up by the system.
The present invention is directed toward a reset circuit for resetting the integrator of an electronic engine spark timing controller which is highly immune to noise and which provides accurate resetting of the integrator at predetermined engine crank angles. By way of example, an electronic spark timing controller of the type having an integrator with which the present invention may be practiced is disclosed in U.S. patent application Ser. No. 388,673 filed Aug. 15, 1973, and assigned to the same assignee as the present application. Features and advantages of the present invention will be seen in the ensuring description and claims which are to be taken in conjunction with the accompanying drawing.